Cash And Cash Equivalents Maturity Period

No definition available.

Name:	issi_CashAndCashEquivalentsMaturityPeriod
Namespace Prefix:	issi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Inventory Aging Period

+ References

No definition available.

+ Details

Name:	issi_InventoryAgingPeriod
Namespace Prefix:	issi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	issi_OrganizationConsolidationandPresentationofFinancialStatementsLineItems
Namespace Prefix:	issi_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Standard Product Warranty Description Warranty Period

+ References

No definition available.

+ Details

Name:	issi_StandardProductWarrantyDescriptionWarrantyPeriod
Namespace Prefix:	issi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount charged to advertising expense for the period, which are expenses incurred with the objective of increasing revenue for a specified brand, product or product line.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 720

-SubTopic 35

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6420018&loc=d3e36677-107848

+ Details

Name:	us-gaap_AdvertisingExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 21

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13537-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 275

-SubTopic 10

-Section 50

-Paragraph 20

-URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6404-108592

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 20

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13531-108611

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 275

-SubTopic 10

-Section 50

-Paragraph 18

-URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6351-108592

+ Details

Name:	us-gaap_ConcentrationRiskPercentage1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Organization and Significant Accounting Policies (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Cash and cash equivalents maturity period	90 days
Inventory aging period	1 year
Option vesting term	4 years
Business segment	1
Period of product warranty	12 months
Largest Distributor \| Sales Revenue, Goods, Net \| Customer Concentration Risk
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Concentration Risk, largest customers (percentage)	17.00%	17.00%	14.00%
Second Largest Distributor \| Sales Revenue, Goods, Net \| Customer Concentration Risk
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Concentration Risk, largest customers (percentage)	13.00%	11.00%	13.00%
Selling, general and administrative
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Advertising costs	$ 84	$ 79	$ 59
Minimum
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Estimated useful lives of purchased definite lived intangible assets	6 months
Maximum
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Estimated useful lives of purchased definite lived intangible assets	8 years
Property and equipment \| Minimum
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Property, equipment and leasehold improvements useful life	2 years
Property and equipment \| Maximum
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Property, equipment and leasehold improvements useful life	10 years
Buildings and leasehold improvements \| Minimum
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Property, equipment and leasehold improvements useful life	30 years
Buildings and leasehold improvements \| Maximum
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Property, equipment and leasehold improvements useful life	50 years
Wafer and Die Bank
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Inventory aging period	2 years